Spatial and Temporal Variability of Precipitation Complexity in Northeast Brazil

In this work, we analyze the regularity of monthly rainfall temporal series during the period 1953 to 2012, recorded at 133 gauging stations in the state of Pernambuco, northeastern Brazil. We use sample entropy method (SampEn), which is suitable for short and noisy data and recently attracted the attention of hydrologists as promising for rainfall studies. By comparing the SampEn values of the analyzed series, we find that for both the original and deseasonalized series entropy increases (regularity decreases) in the west-east direction from the inland Sertao region towards the coastal Zona da Mata. SampEn values for the semiarid Sertao region are significantly different from the humid coastal Zona da Mata and subhumid transition Agreste regions. By comparing two 30 year subperiods (1953-1982 and 1983-2012), we found that in the second period, the rainfall amount decreases in Sertao and Agreste, and increases in Zona de Mata, and that the Agreste and Zona da Mata regions become more similar in respect to the regularity of rainfall dynamics. In the second subperiod, the rainfall regime changes the most in Zona da Mata (both original and anomalies series show a significant difference in SampEn values). By analyzing time dependent SampEn, we identified several periods of increasing entropy, which are related to specific climatic phenomena such as subsequent El Nino and La Nina episodes. This work represents a contribution to establishing the use of information theory-based methods in climatological studies.

Automated summary

In this work, the regularity of rainfall temporal series in the state of Pernambuco, northeastern Brazil, from 1953 to 2012 was analyzed using the sample entropy method (SampEn). The study found that the regularity of rainfall decreases from the inland Sertao region towards the coastal Zona da Mata region. The analysis of different time periods and comparison of regions showed variations in rainfall amount and regularity, which were associated with specific climatic phenomena such as El Nino and La Nina episodes. This study contributes to the application of information theory-based methods in climatological studies.